The villages downwind of Mayak were farming villages — small places along the Techa and out toward Kamensk-Uralski, people growing food and drawing water. In 1957 a tank of high-level liquid waste under the plant lost its cooling. That waste generates heat continuously as it decays; the cooling system is what carries the heat away. When it failed, the liquid boiled dry, the residue heated further, and the tank blew its concrete lid off, throwing contamination north-east in a long, narrow band. The relief map attached shows that band, thinning as it goes.
About 10,000 people were eventually moved, some of them not for a year or more, and they were not told why. The accident was concealed for close to two decades, so families living on contaminated land had no way of knowing what had settled on it. The health effects were followed later, imperfectly, by people who had to work backwards from what was left.
The Soviet government didn't acknowledge it publicly until 1989. Western analysts had already worked much of it out from published Soviet research papers and maps that quietly stopped naming villages — but the people living on that land had nothing to work from.
The closed land north-east of the plant became the East Urals Nature Reserve in 1968, and a long run of animal studies came out of it — voles, mostly, generation after generation, counted by people who could not say where they were working. Knowledge gathered from a place nobody should have had to leave.